Enhancement equipment for connection to electronic musical instruments

ABSTRACT

Spatial enhancement equipment for connection to existing organs or other electronic musical instruments comprises an artificial reverberation unit having coiled springs and an input transducer including a driving coil. The connection of the driving coil to the output amplifier of the organ includes a series connection of a photoresistor having a capacitor shunted across it. A variable light source applies pulses of light to the photoresistor alternately to cause it to conduct and not conduct. When the photoresistor is not conducting the electrical signals from the organ are applied to the driving coil through the shunt capacitor, introducing a phase shift into the signal. The variable light source is disclosed as a rotating disc having different patterns of opacity on it. A gating arrangement connected in parallel with the reverberation unit prevents noise from activating the power amplifier of the enhancement equipment in the absence of musical input. The gating arrangement includes a gating amplifier driving a filamentary bulb optically coupled to a photoresistor connected between the preamplifier and power amplifier of the enhancement equipment.

United States Patent [191 Pavia ENHANCEMENT EQUIPMENT FOR CONNECTION TO ELECTRONIC MUSICAL INSTRUMENTS [76] Inventor: Leonard W. Pavia, 460 Columbia Tnpk., Florham, NJ. 07932 [22] Filed: Oct. 5, 1972 [21] Appl. No.: 295,361

Related US. Application Data [63] Continuation-impart of Ser. No. 145,856, May 21,

1971, abandoned.

[ Mar. 26, 1974 11/1971 Sharp 84/124 3,626,078

12/1971 Sekiguchi 84/125 X [57] ABSTRACT Spatial enhancement equipment for connection to existing organs or other electronic musical instruments comprises an artificial reverberation unit having coiled springs and an input transducer including a driving coil. The connection of the driving coil to the output amplifier of the organ includes a series connection of [52] U-S- Cl a photoresistor having a capacitor shunted across it. A 26 variable light source applies pulses of light to the pho- [51] Int. Cl. G101] 1/02 toresistor alternately to cause it to conduct and not 1 Field of Search conduct. When the photoresistor is not conducting the 1310- 179/1 1 1 electrical signals from the organ are applied to the 1 J driving coil through the shunt capacitor, introducing a phase shift into the signal. The variable light source is References Cited disclosed as a rotating disc having different patterns of UNITED STATES PATENTS opacity on it. A gating arrangement connected in par- 2,230,836 2/1941 Hammond 179/1 M i the reverberatm", Prevents noise fmm 3,267,198 3/1966 Hurvitz u 34/124 activating the power amplifier of the enhancement 3,325,581 6/1967 Young 84/].24 equipment in the absence of musical input. The gating 3,405,223 /1968 Pavia l 84/].18 arrangement includes a gating amplifier driving a fila- 13,403 1 1/1968 Jacob n 8 mentary bulb optically coupled to a photoresistor con- L i r nected between the preamplifier and power amplifier au e f th ha t 3,492,425 1/1970 Evans 179/] .l o 6 en ncemen eqmpmel? 3,609,205 9/1971 Schwartz et a1. 84/1.18 X 10 Claims, 4 Drawing Figures 1i] 1 31 U 37 ELECTRONIC f L 0RGAN 1 *1 VARlABLE LIGHT 33 SOURCE 24 18 TI 27 23'? [6 l I f 2| .163 r k 26 64 PREAMP 27 L Z3 26 I6 lg 65 AN 6| AMP 68 We "$81115; 5; I \Q 3: v v 'vv'v z I :11 l a, 66 l g 5 :2 :z 5 \g 81 1 Fr oWER I 1 SUPPLY 1 E 1 75 r- GATE VOLUME LGATE AMPLIFIER L CONTROL ENHANCEMENT EQUIPMENT FOR CONNECTION T ELECTRONIC MUSICAL INSTRUMENTS RELATED APPLICATION This application is a continuation-in-part of my copending U.S. Pat. application Ser. No. 145,856, filed May 21, 1971, now abandoned.

BACKGROUND OF THE INVENTION Electronic organs have become very popular in recent years as musical instruments. Electronic organs can produce many sounds with the versatility one associates with pipe organs, including simulating numerous types of instruments or combinations of instruments. Additionally electronic organs are much less expensive then the older and traditional pipe organs.

Unfortunately, most electronic organs have produced their own unique sounds which are distinct from those provided by pipe organs. Specifically, the electronic organ has generally not succeeded in reproducing the grandeur and spatial sounds of the pipe organ. Particular areas where electronic organs have not completely reproduced the sound of pipe organs con- .cern the spatial quality, chorusing, quality of the voicing and reverberation. Reverberation occurs because pipe organs have usually been played in large rooms which are acoustically reverberant. Electronic organs, which are frequently placed in a persons home, are less likely to be located in rooms having this particular acoustic environment.

Various techniques and equipments have been proposed to improve the sound characteristics of electronic organs. To improve the random sound character resulting from slight differences in the pipes, a random tone generator may be employed, as described in my U.S. Pat. No. 3,405,223, Oct. 8, 1968. To provide a degree of reverberation a reverberation unit as dis- In accordance with an aspect of my invention the driving coil of the input transducer is thus connected in parallel with the speaker of the electronic organ. Connected in series in one of theinput leads to the driving coil is a photosensitive resistor having a capacitor connected in parallel therewith. A variable light source applies light to the photoresistor, the photoresistor having a relatively low resistance when light is applied to it and a relatively high resistance when the photoresistor is not illuminated.

Since the external reverberation device of my invention is in parallel with the output leads between the output amplifier of the electronic organ and the speaker of the organ, only a small portion of the output signals from the organ will be applied to my device. However, this small portion is amplified to be a signifcant part of the total sound. The sound reinforcement through the speakers of my device thus adds to the sound from the main speakers of the organ. This addition gives the sound greater depth, greater spatial characteristics, increased reverberation, and an element of closed in Hammond U.S. Pat. No. 2,230,836, Feb. 4, I

1941, and further in my U.S. Pat. No. 3,564,106, Feb. 16, 1 971, maybe utilized.

The difficulty with these priorarrangements is that they must be placed in the organ initially'when it is built or require substantial rewiring of an organ if they are to be added to an existing electronic organ.

It is therefore an object of my invention to provide a reverberation device which adds tone color, smooths out the sound, adds the spatial sound effect one expects from reverberation with pipe organs, may be connected to existing organs without rewiring of the organ,.is insensitive to noise, and does not have an overly long reverberation signal length.

SUMMARY OF THE INVENTION transducer; such reverberation unitsare described,

inter alia, in A. C. Young U. S. Pat. No. 3,106,610, Oct. 8, 1963, and my prior U.S. Pat. No. 3,564,106, Feb. 16,1971.

air motion.

This is particularly obtained because of my unique arrangement of an on-off switch shunted by a capacitor in the input lead to the drive coil of the reverberation unit. I have found that the capacitor together with the inductance of the driving coil of the input transducer comprise a tuned circuit. The result of this is to introduce a phase shift in the electrical signal applied to the reverberation unit through the capacitor.

Accordingly, in operation, when light is impinging on the photoresistor, the signal from the output amplifier of the electronic organ is applied directly through the conducting photoresistor to the reverberation unit input driving coil. When the light is not impinging the photoresistor, the resultant high impedance prevents the electrical signal from following this path. Instead the signal now passes through the capacitor connected in parallel with the photoresistor. The result is that the level of the input signal to the reverberation unit is lower but more significantly, as discussed above, it undergoes a phase shift. It is this phase shift particularly that provides the spatial effect desired.

Because the enhancement device in accordance with my invention would be activated by noise levels of the organ when it is not being played as well as by internal noise within the enhancement device itself, I provide, in accordance with another aspect of my invention, an automatic gating circuit to gate signals through my enhancement device only when the organ is actually being played. Specifically the phase shifted signal is also applied to a gating control arrangement in parallel with the reverberation device. The gating control arrangement includes a gate volume control circuit, allowing the gating point to be individually set for each organ, a gate amplifier whose output causes illumination of a filamentary lamp, and an amplifier volume control circuit. The output of the reverberation unit is applied to a preamplifier having serially connected in its output a photoresistor optically coupled to the filamentary lamp of the gate control arrangement. When the photoresistor is in its high impedance state the preamplifier can not drive the final power amplifier of my enhancement device.

By adjusting the gate volume'control circuit, the player arranges the enhancement device in accordance with my invention so that no output occurs from the enhancement device for maximum noise output from the organ in the absence of music. Under these conditions the input to the gate amplifier is insufficient to turn the output lamp on. However, as soon as music is played, the lamp is turned on and the enhancement device of my invention is activated.

However, when the music stops, there is a decay time during which the lamp remains first bright enough and then warm enough to maintain the conductive coupling between the preamplifier and the power amplifier due to the infrared sensitivity of the photoresistor. This decay closely approximates the decay time of an organ pipe. Because the power to the lamp is removed as soon as the musical signal ceases, the enhancement signal through the reverberation unit is not unduly long, but itself will cease after this short delay for the lamp filament to cool down.

Advantageously, in accordance with my invention the musical effect is enhanced not only because of the phase and amplitude shift due to the capacitor and photoresistor in the input loop of the reverberation unit but also due to a capacitor connected across the coil of the output transducer, providing a resonant effect, and due to the preamplifier clipping the output signals from the output transducer, all of these effects cooperating for the desired musical sound.

In one specific illustrative embodiment I employ as the variable light source a lamp and a rotating disc on which are positioned different patterns of opacity and translucency, depending on the sound effect desired. Further by employing a disc the sound effect of the organ can readily be changed by a simple substitution of one disc for another. Specifically, the disc may have a number of alternate areas of opacity and translucency, the areas being of equal sizes; in one specific embodiment twelve such alternate areas are provided. In this specific embodiment with a disc rotation at a speed of 45 revolutions per minute, nine light pulses every two seconds are provided impinging on the photoresistor.

Alternatively, the disc may have areas of different degrees of opacity, shaded from translucent to fully opaque. This provides, at a speed of 45 revolutions per minute, one light pulse per one and one-third seconds. But whereas in the prior disc arrangement the pulses are sharp edged, being substantially square waves, in this arrangement the pulse has a gradual amplitude increase, causing a substantially sinusoidal wave form; the disc may be shaded from opaque to translucent both for its leading and trailing edges, or it can drop from opaque to translucent sharply, in which case the trailing edge is also sharp.

Multiple patterns may be present on the same disc,

cooperating with different photoresistors, in which case a switch may be advantageously provided to allow selection of the particular photoresistor, and thus the particular light pattern, employed with the phase shift network and the reverberation unit.

To provide improved sound characteristics in one embodiment I utilize two photoresistors in parallel, thereby further lowering the resistance when the light impinges. But further, for a gentle effect I position the photoresistors at an angle to a radius from the center of the rotating disc. In this way the light does not equally impinge'on the photoresistors but instead initially impinges only one, then both, and then only the other.

If sharp light pulses on the photoresistors are desired I utilize both a screen or mask between the rotating disc and the light source and also collars or shields on the photoresistors and I align the photoresistors with the radius from the center of the disc. This prevents stray light from exciting the photoresistors and increases the sharpness of the pulse. The screen has an aperture in it shaped to match the photoresistors positioned behind the disc. If a smoother transition is desired for the gentle effect discussed above, I omit the collars and the screen and allow some stray light to lower the resistance of the photoresistors before they are directly impinged by the light.

In operation, when the light is impinging the photoresistors, the signal from the output amplifier of the electronic organ is applied directly through the photoresistors to the reverberation unit input transducer driving coil. When the light is not impinging the photoresistors, the resultant high impedance prevents the electric signal from following this path. Instead the signal now passes through the capacitor connected in parallel with the photoresistors. I have found that the capacitor changes the input to the coil dependent on the frequency of the signal, thereby introducing a degree of frequency selectivity in the phase shift network.

If different widths of opaque and translucent bands are employed, then the ratio of normal signal to lessened signal is changed. The phase shift effect in accordance with my invention is still present but the durations of the direct and phase shifted input signals are changed consistent with the change in pattern on the disc.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic representation of one illustrative embodiment of my invention as connected to an electronic organ;

FIG. 2 is a plan view of the rotating disc employable in the variable light source of the embodiment of FIG. ll;

FIG. 3 is a diagram illustrating the physical positioning of the photoresistors behind the rotating disc in one embodiment of my invention; and

FIG. 4 is a side view of the variable light source and photoresistors in the embodiment of FIG. 1.

DETAILED DESCRIPTION Turning now to the drawing, there is depicted in FIG. I one specific illustrative embodiment of my invention as connected to an electronic organ 10. It is to be understood of course that a spatial enhancement device in accordance with my invention can be utilized with many different types of electric or electronic musical instruments but I have found that my invention is particularly useful'in enhancing the spatial sound characteristics of electronic organs.

As is known in the art an electronic organ includes an output amplifier 11 connected to the output speaker 12 by output leads 13. My invention is advantageously bridged across the leads 13 so that a portion of the energy from the output amplifier 11 is diverted away from the speaker 12 and into the spatial enhancement device of my invention.

My spatial enhancement device includes an artificial reverberation unit of a type known in the art; in this specific embodiment I employ a unit of the general type shown in Hammond US. Pat. No. 2,230,836, Feb.

4, 1941, wherein coiled springs 16 are caused to vibrate in response to the electrical signals representing the musical tones. An input electromechanical trans ducer 17 serves as an input driver to launch the mechanical signals onto the springs in response to the applied electrical signals. An output electromechanical transducer 18 serves as the output pickup device for receiving the mechanical vibrations from the springs and converting them again to electrical signals for application, through a preamplifier 60, amplifier volume control 61, and power amplifier 20, to the separate output speaker 21 of the device; the preamplifier 60 advantageously clips the output signals from the output transducer 18.

The transducers, which may be of any of several types known in the art, include a coil 23 wound on a core, not shown, so as to define a magnetic circuit includingthe annular laminations 24; while only the input transducer 17 has been depicted in detail, as my invention is particularly concerned with the application of the input signals to that transducer, the output transducer 18 is similar, as is known. Positioned within the magnetic circuits thus defined are highly compliant wires, such as of beryllium copper, whose ends 26 are bent in the form ofa hook. Each of these wires extends into and is supported by a tubular housing 27; further as is known in the art, a small diameter annular permanent magnet, not shown, surrounds the end 26 of each of the wires and is positioned within the magnetic circuits of the laminations 24.

Extending between the hooks 26 of the input and output transducers 17 and 18 are the spring elements 16 which may advantageously be of slightly different lengths or number of turns so as to have slightly different transmission characteristics.

When the output signals from the organ amplifier 11 are applied to the organ speaker 12, advantageously a portion of the output signal is applied over leads 30 and 31. Because the spatial enhancement device in accordance with my invention contains its own amplifier I can balance the sound outputs from the speakers 12 and 21 to get any desired ratio of straight sound to enhanced sound; the exact proportion will depend somewhat on the effects desired. I have found it satisfactory in some instances to have the sound actually evenly divided between the two speakers.

It should also be pointed out that while I have depicted only a single output amplifier 11 for the organ, in actuality there may be a number of separate output channels in the organ. For home instruments it may be advantageous to apply all of these organ outputs to a mixer circuit and apply the output of the mixer to my spatial enhancement device. Alternatively for a church organ it may be desirable to provide a separate spatial enhancement device in accordance with my invention for each organ channel.

In accordance with an aspect of my invention the input coil 23 of the driving transducer 17 is connected 7 to the leads 13 by an arrangement which affects the input signal. Specifically in lead 31 are connected a switch device 33 having a capacitor 34 connected across it. The switch device 33 is arranged to be alternately conductive and non-conductive. In this specific illustrative embodiment the switch device 33 comprises a pair of parallel connected photoresistors, as of cadmium sulfide cells. These cells have an impedance of the order of 5 megohms when light is not impinging on them and of the order of 50-75 ohms when conductive. Since I utilize two in parallel the resistance introduced when they are conductive is only of the order of 25 ohms.

In this specific illustrative embodiment I employ a variable light source 37, described further below, to turn the switching elements 33 on and off. It is to be understood however that various other switching devices might be employed. I have found the light actuated elements to be particularly advantageous as they do not introduce any electrical noise or clicks into the signal, which noise is increased due to the effects both of the reverberation unit and the final amplification. Accordingly, my preferred embodiment incorporates the light actuated switching elements as disclosed.

Leaving aside the mechanism of the variable light source and my gating control circuitry, for the moment, let me describe the basic operation of my invention. When the switch 33 is conductive due to light from source 37, the switch element provides a low impedance path for the signal from the amplifier 11 to the drive coil 23 of the input transducer 17. However, when the switch 33 is in its high impedance state, that is, when no light is being emitted by the light source 37, the input signal is not blocked from the drive coil 23. Instead the input signal is diverted from the switch 33 and flows through the parallel capacitor 34. The signal passing through the capacitor I have found to be diminished in amplitude but more significantly to have its frequency characteristic altered; more specifically I believe the signal undergoes a phase shift, dependent upon the frequency components of the output signal from the organ, the magnitude of the capacitor, and the inductance of the coil 23. In one specific illustrative embodiment I have employed a .22 microfarad capacitor for capacitor 34.

By pulsing the switching element 33 I can accordingly obtain a celesta effect in the total sound, with the sound from speaker 21 alternately reinforcing and cancelling the sound from speaker 12. Further by the placement of the speakers relative to the listener and by choice of the driving of the switch 33 I can attain various other effects. The overall effect, particularly for an organ, is that the enhancement device in accordance with my invention adds a spatial and a chorusing quality to the sound, improves the voicing effect and provides an impression of space such as one expects from an organ in a large acoustically reverberant room. In fact organs whose own sound outputs are rela tively flat and very electrical sounding can readily be made to sound spatial and more like a true pipe organ.

A reverberation unit such as employed herein is very sensitive to various types of noise, including motor noise, room noise, amplifier noise, and noise present in the organ as well as in the enhancement device. When a signal is being applied to the reverberation unit this noise is generally masked and is not heard. However, when no input signal is applied this noise is still present and may be transmitted along the reverberation unit, amplified, and reproduced by the speaker 21. In accordance with another aspect of my invention, a gating arrangement is employed to prevent the occurrence of any noise output signal under these conditions.

Specifically, in this specific illustrative embodiment as depicted in FIG. 1, the input signal from the phase shift circuitry of capacitor 34 and switch 33 is applied not only to the input coil 23 of the transducer 17,

thereby to define the resonant circuit, but also over leads 63,64 to a gate volume control circuit 65 comprising a potentiometer 66. The purpose of the gate volume control circuit will become apparent from the further description below.

The gate control signal is then applied over leads 68,69 to a gate amplifier circuit 70, the output of which activates a small filamentary bulb 71, located in the amplifier volume control circuit 61. The gate circuit amplifier may advantageously have a small power output, as of the order of one watt, and should have a logarithmic output characteristic rather than a linear characteristic. In this way the amplifier reaches its maximum output power and then flattens out so that the small bulb 71 does not burnout. A power supply 75 powers the gate amplifier 70, as is known in the art.

The output transducer 18 of the reverberation unit applies the modified signal to a preamplifier 60, which may be of any of many known designs but which clips the signals applied to it. I have found it desirable that a capacitor 77 be across the coil 23 of the output transducer so that a resonant peak occurs in the signal to the preamplifier 60. In accordance with an aspect of my invention, the output of the preamplifier 60 is connected to the power amplifier through an amplifier volume control circuit 61 including a potentiometer 81, a light sensitive or photoresistor 80, and the output filamentary bulb 71 connected to gate amplifier 70. Theoutput of the amplifier volume control circuit 61 is connected through the power amplifier 20 to the speaker 21.

The gate volume control circuit 65, gate amplifier 70, and amplifier volume control circuit 61 thus define, in accordance with this aspect of my invention, a selfactivating optical gating circuit, whereby the enhancement equipment of my invention is virtually silent when the organ is not playing, the equipment being in a waiting condition with the volume automatically turned off. However, when the musician plays the instrument, the enhancement equipment immediately comes into action; which the musician stops playing, the enhancement equipment will gradually turn itself off, this taking approximately a half second on average volume to one full second on louder volume levels. This delay in turn off occurs because the filamentary lamp 71 continues to radiate, particularly infrared, after there is no output from the gate amplifier 70. I have found that the decay caused by the cooling down of the lamp filament to be substantially identical to the decay in signal in a pipe organ, thereby further enhancing the sound effects of the electronic organ.

Since each organ to which my invention may be connected presents its own noise level, the gate volume control circuit allows the automatic gating arrangement to be regulated for each instrument so that the enhancement equipment does not transmit any noise signals when the organ is not being played. In operation, the player of the organ initially depresses the volume pedal of the organ fully so that it generates the maximum amount of residual noise that the organ is capable of producing. The player then adjusts the potentiometer 66 of the gate circuit 65 to its off position so that no signal at all will be applied to the input of the gate amplifier 70. The player then slowly turns the potentiometer control until the enhancement equipment is just activated and noise output appears at speaker control until the noise just ceases coming from the speaker 21. At this point, the automatic gate control is fully adjusted for the particular organ to which my invention is connected.

I have found that when the organist is playing soft tonalities, the enhancement equipment in accordance with my invention will produce an air noise quality which enhances the tonalities of the soft wind stops; this air noise effect is due to noise effects within the preamplifier 60 and the power amplifier 20 of the enhancement equipment itself. On higher volume levels, this windy quality tends to be absorbed, and is not noticeable to any large extent, but is still always present, adding its own unique characteristics. However, in all cases, because of the automatic gating provided by my invention, and specifically by the arrangement including the filamentary bulb 71 in the amplifier volume control circuit,'noise is not present when the organ is not being played and a pipe organ decay characteristic is attained.

The potentiometer 81 in the volume control circuit 72 allows the player to adjust the volume output of the enhancement equipment in accordance with my invention in accordance with the particular organ and room in which he is playing, since the degree of volume desired is generally a matter of personal taste of the player.

In the specific illustrative embodiment of my invention depicted I utilize a rotating disc to create a variable light source 37. Various other variable light sources may be employed, such as logic or digital circuitry which turns on and off a light in various timed patterns. I have found a rotating disc however to offer certain advantages, including ease of changing from one pattern of light pulses to another and accurate control of the time of switching. Specifically, as depicted in FIG. 4, the variable light source includes a bulb 40, a rotating disc 41 driven by a motor, not shown, a mask or screen 42, and the photoresistors 33 at the bottom of shields or collars 43, as depicted for one pair of photoresistors, or without such shields or collars, as depicted for another pair of photoresistors. The reason for this difference will be discussed below.

The disc 41 is itself of a translucent material and, as seen in FIG. 2, can have various patterns of translucent and opaque areas. Specifically, the particular disc depicted in FIG. 2 has an outer ring of alternate areas 45 and 46 which are of equal size and are, respectively, opaque and translucent. If the disc is driven at a rate of 45 revolutions per minute there are therefore developed light pulses of equal duration at a rate of nine pulses every 2 seconds for the l2 area pattern depicted. Alternatively, if seven alternate pairs of areas 45 and 46 are employed, light pulses occur at a rate of 5 and A pulses per second. To prevent stray light from impinging on the photoresistors 33c and 33d before the translucent pattern 46 is directly above the photoresistor, I provide the mask or screen 42 between the disc 41 and bulb 40 and I also provide the collars 43 in order to obtain sharp signals.

Alternately, a different sound effect may be obtained if the light pulses are not sharp edged but provide smoother transitions. In this instance the inner ring of disc 41, FIG. 2, may be employed. As there depicted, the opaque area 50 is about 40 percent of the total area. Opposite that is a translucent area 53 of about 25 percent of the area. Between the two is a short transition area 51 of about 10 percent of the area and a longer area 52 of about 25 percent of the area. In this instance, as seen in FIG. 4, no collars are provided on the photoresistors 33a and 33b and no mask 42 is utilized as some light leakage onto the photoresistors is desired.

I have found that the outer ring may advantageously be used when a large theatre effect :is desired. Normally in electronic organs vibrato is provided at a rate of about seven or eight pulses per second. Sound therefore comes out of the organ speaker 12 and also out of the speaker 21 with this vibrato imposed on it. The enhancement device of my invention, if 14 equal areas are utilized for the disc pattern, causes the sound to be shifted by the 5 and A pulses per second phase shift. In the air an acoustic coupling occurs so there is a doubling effect, that is, the organ sound through the speaker 21 is effected directly and then the sound from the speaker 12 is effected in air by the sound from the speaker 21. For this it is desirable both to have the faster pulse rate and the sharper pulses.

On the other hand when softer and subtler sounds are desired, the inner pattern on disc 41 may be utilized with gentler pulses at the slow speed; Electronic organs have various imperfections, particularly resulting in beat frequencies in the output. A gentler phase shift serves to smooth over these beats. In this instance, the signal through the speaker 12 has its imperfections masked by the slow phase shift effect from the speaker 21.

Advantageously a manual switch can be provided to insert either pair of photoresistors of FIG. 4 into the circuit of FIG. 1. It is apparent that additional patterns can be provided on the disc 41, each pattern cooperating with a different pair of photoresistors and each being selectively chosen by the user of the instrument.

I have found that a multitude of different spatial effects may be attained by varying the patterns on the disc and by changing the speed of rotation of the disc. One advantage of the disc as a control for the light source is in fact this degree of flexibility, if not to the user at least to the manufacturer who can readily tailor the sound effect of the enhancement device in accordance with my invention to the particular use to which it is to be put and to the particular musical instrument and room in which it is to be located.

In accordance with another aspect of my invention, the mounting of the photoresistors may also be utilized to determine the character of the light signal impinging .on the photoresistors. Thus as seen in FIG. 3, the photoresistors 33a and 33b are mounted for a gradual effect of the light whereas photoresistors 33c and 33d are mounted for sharp edged signals. Thus if one considers a radius of the disc as passing between the photoresistors 33a and 33b, these photoresistors are at an acute angle to that radius. This further assures the gradual effect of the light on these photoresistors; it is to be re membered that, as seen in FIG. 4, no collars 43 or mask 42 is utilized with these photoresistors. Advantageously, the light first impinges on one of these photoresistors, then both of them, and finally the other photoresistor alone. In contradistinction, photoresistors 33c and 33d are aligned with a radius of the disc so that the light impinges each equally. This further assures the sharp edged signals desired with these photoresistors.

While I have depicted one specific embodiment of my invention, it is to be understood that various modifications may be made without departing from the spirit and scope of my invention. Thus, as indicated, other switching devices may be employed for connection in the lead 31, provided they introduce no noise into the electrical signals, and other control mechanisms can be employed for controlling the switching devices. Similarly, the degree of the change in frequency characteristic due to the capacitor 34, the relative amounts of the signals, the frequency and phase shift of operation of the switching device and the amount of reverberation introduced, as by the springs 16, can all be varied at the will of the designer and player of the instrument for the maximum sound effect he desires.

Specifically, the variable light source 37 may include a light bulb controlled by a relaxation oscillator, the light being turned on and off at the rate of the oscillator. In such an embodiment, different light bulbs and oscillators would be employed for the different photoresistors.

What I claim is:

1. A musical enhancement device for connection to electronic musical equipment having an output amplifier connected by a pair of leads to a speaker, said device comprising a reverberation unit including means for transmitting a mechanical signal, an input transducer including a coil for launching said mechanical signal in response to an electrical signal, and an output transducer,

an amplifier arrangement connected to transducer,

a separate speaker connected to said amplifier arrangement,

an input loop for connection across the pair of leads from the output amplifier of the equipment, said input loop comprising a capacitor in series with said coil,

a switch device connected in parallel with said itor,

means for controlling said switch device, whereby said capacitor and coil being directly connected together in said input loop alter the characteristics of the signal applied to said mechanical signal transmitting means so that the sound from said separate speaker undergoes both amplitude and phase modulation,

a gating control arrangement connected to said coil of said input transducer by an adjustable gate volume control device so as to be responsive to signals from the output amplifier of the equipment for controlling said amplifier arrangement, said gating control arrangement including a gate amplifier connected to said gate volume control device, and

a lamp connected to the output of said gate amplifier,

said output capac- 2. A musical enhancement device in accordance with claim 1 wherein said adjustable gate volume control device includes an adjustable resistor connected across coil of said input transducer and said gate amplifier comprises an amplifier having a logarithmic output characteristic.

3. A musical enhancement device in accordance with claim 1 wherein said amplifier arrangement includes a preamplifier and a power amplifier, said volume control arrangement is connected between said preamplifier and said power amplifier, and said lamp is a filamentary lamp.

' 4. A musical enhancement device in accordance with claim 3 wherein said output transducer includes a coil and a capacitor connected across said coil, said coil being connected to said preamplifier.

5. A musical enhancement device in accordance with claim 1 wherein said switch device includes a photosensitive element and said controlling means includes means for applying pulses of light to said photosensitive element.

6. A musical enhancement device in accordance with claim 5 wherein said photosensitive element is a photoresistor and said light pulse applying means includes a disc having areas of different light transmitting characteristics.

7. A device for connection to an electronic organ comprising means for transmitting a mechanical signal, an input transducer including a coil for launching said mechanical signals in response to electrical signals, means for connecting said input transducer to the organ, said connecting means including a switch device connected between the organ and said input transducer, means for controlling said switch device, and a capacitor connected in parallel with said switch device between the organ and said input transducer for providing a phase shift and amplitude shift of the electrical signals when said switch device is not conductive,

an output transducer for generating output electrical signals in response to said mechanical signals,

an output arrangement connected to said output transducer and including an output amplifier and an amplifier volume control circuit, and

a control arrangement 1 for blocking output signals from said output transducer to said output amplifier in the absence of a musical signal from the organ, said control arrangement including means for controlling said amplifier volume control circuit, means for energizing said last mentioned means, and adjustable means for connecting said energizing means to said means for connecting said input transducerto the organ 3. A device in accordance with claim 7 wherein said switch device comprises a photosensitive element connected to said coil, and said controlling means includes means for applying light pulses to said photosensitive element.

9. A device in accordance with claim 7 wherein said amplifier volume control circuit includes a photosensitive element, and said energizing means includes a gate amplifier, a filamentary bulb connected to the output of said gate amplifier as to be powered thereby, the light from said bulb being coupled to said volume control circuit photosensitive element.

10. A device in accordance with claim 9 wherein said output arrangement includes a preamplifier, said amplifier volume control circuit being connected between the output of said preamplifier and the input of said output amplifier, and said preamplifier clips said output electrical signals from said output transducer, and further comprising a capacitor connected across said output transducer.

* fi t 

1. A musical enhancement device for connection to electronic musical equipment having an output amplifier connected by a pair of leads to a speaker, said device comprising a reverberation unit including means for transmitting a mechanical signal, an input transducer including a coil for launching said mechanical signal in response to an electrical signal, and an output transducer, an amplifier arrangement connected to said output transducer, a separate speaker connected to said amplifier arrangement, an input loop for connection across the pair of leads from the output amplifier of the equipment, said input loop comprising a capacitor in series with said coil, a switch device connected in parallel with said capacitor, means for controlling said switch device, whereby said capacitor and coil being directly connected together in said input loop alter the characteristics of the signal applied to said mechanical signal transmitting means so that the sound from said separate speaker undergoes both amplitude and phase modulation, a gating control arrangement connected to said coil of said input transducer by an adjustable gate volume control device so as to be responsive to signals from the output amplifier of the equipment for controlling said amplifier arrangement, said gating control arrangement including a gate amplifier connected to said gate volume control device, and a lamp connected to the output of said gate amplifier, said amplifier arrangement including an amplifier volume control arrangement including a photosensitive element responsive to said lamp.
 2. A musical enhancement device in accordance with claim 1 wherein said adjustable gate volume control device includes an adJustable resistor connected across coil of said input transducer and said gate amplifier comprises an amplifier having a logarithmic output characteristic.
 3. A musical enhancement device in accordance with claim 1 wherein said amplifier arrangement includes a preamplifier and a power amplifier, said volume control arrangement is connected between said preamplifier and said power amplifier, and said lamp is a filamentary lamp.
 4. A musical enhancement device in accordance with claim 3 wherein said output transducer includes a coil and a capacitor connected across said coil, said coil being connected to said preamplifier.
 5. A musical enhancement device in accordance with claim 1 wherein said switch device includes a photosensitive element and said controlling means includes means for applying pulses of light to said photosensitive element.
 6. A musical enhancement device in accordance with claim 5 wherein said photosensitive element is a photoresistor and said light pulse applying means includes a disc having areas of different light transmitting characteristics.
 7. A device for connection to an electronic organ comprising means for transmitting a mechanical signal, an input transducer including a coil for launching said mechanical signals in response to electrical signals, means for connecting said input transducer to the organ, said connecting means including a switch device connected between the organ and said input transducer, means for controlling said switch device, and a capacitor connected in parallel with said switch device between the organ and said input transducer for providing a phase shift and amplitude shift of the electrical signals when said switch device is not conductive, an output transducer for generating output electrical signals in response to said mechanical signals, an output arrangement connected to said output transducer and including an output amplifier and an amplifier volume control circuit, and a control arrangement for blocking output signals from said output transducer to said output amplifier in the absence of a musical signal from the organ, said control arrangement including means for controlling said amplifier volume control circuit, means for energizing said last mentioned means, and adjustable means for connecting said energizing means to said means for connecting said input transducer to the organ
 8. A device in accordance with claim 7 wherein said switch device comprises a photosensitive element connected to said coil, and said controlling means includes means for applying light pulses to said photosensitive element.
 9. A device in accordance with claim 7 wherein said amplifier volume control circuit includes a photosensitive element, and said energizing means includes a gate amplifier, a filamentary bulb connected to the output of said gate amplifier as to be powered thereby, the light from said bulb being coupled to said volume control circuit photosensitive element.
 10. A device in accordance with claim 9 wherein said output arrangement includes a preamplifier, said amplifier volume control circuit being connected between the output of said preamplifier and the input of said output amplifier, and said preamplifier clips said output electrical signals from said output transducer, and further comprising a capacitor connected across said output transducer. 